Nowadays, there is an increasing interest to replace conventional fluorescent lamps with LEDs (light emitting diodes) in LCD backlighting and other lighting applications. Generally, LEDs need a driver to provide a controllable current. Moreover, in some applications, power supply voltages, such as 12V, 5V etc. are further needed for other circuits or chips.
FIG. 1 illustrates a prior art LED driver wherein two individual DC/DC switching converters are involved. The first DC/DC switching converter is configured to generate a driving current for LEDs, while the second DC/DC switching converter is configured to provide a power supply voltage Vps for other circuits or chips.
Since the LED driver shown in FIG. 1 needs two high voltage DC/DC switching converters, its size is large and it also suffers from high cost.